Abstract
Recently we demonstrated that crowding also occurs in the time domain: target identification is impaired when other items appear before and/or after the target, at the same location. Such temporal crowding emerged even when the SOA between the target and the preceding and succeeding stimuli was longer than 400 ms. These long-lasting temporal effects did not depend on temporal or spatial uncertainty, but they were reduced when target location was attended. Interestingly, we did not find an interaction between spatial and temporal crowding. In the current study we employed a continuous measure of perceived orientation to examine the nature of the impairment brought about by temporal crowding. A single trial included a sequence of three randomly oriented stimuli presented at 9° of eccentricity. The target was always the second stimulus. SOAs varied between 175 to 475 ms. The stimuli sequence was followed by a probe, and the participants had to rotate it to reproduce the target's orientation. The measure of performance was the angular difference between the target's original and reported orientation. A mixture-model analysis revealed significant effects of SOA on the observers' orientation report precision and on the rate of reporting the orientation of a non-target item, but there was no significant SOA effect on guessing rate. These findings suggest that temporal crowding, like spatial crowding, impairs the precision of encoding processes and increases substitution rate, but does not affect signal-to-noise ratio. This pattern of results is different from that found previously with classical forward and backward masking – classical masking affected mainly signal-to-noise ratio and precision, but did not affect the rate of reporting a non-target orientation. These different patterns of results suggest that temporal crowding is not merely 'particularly long' masking effects, but rather involves different processes.
Meeting abstract presented at VSS 2018